I was looking for some write ups or pictures of none creeping manifolds and stumbled on this.

You are right about the angle of the wastegate, however the explanation isnt quite right.
There is no difference between 'built up pressure' and 'flow pressure', there is just 'pressure' and 'flow'.

Im gonna see if i can sort this out once and for all.

\begin{lecture}

First lets talk about pressure.

As the engine runs, it pumps exhaust gasses into the manifold. The pressure in the manifold is created by the restriction of the turbo. The higher the pressure inside the manifold, the more gas can force itself out through the turbo. The pressure in the manifold will increase until it reaches a point where the amount of gas leaving the manifold is equal to the amount of gas entering the manifold.

When we have reached our deisred boost pressure we open the wastegate to provide an alternate exit for this gas as we dont want any more energy going to the turbo. When the wastegate opens, some of the gas in the manifold will leave via this new route. The smaller the restriction in the wastegate route, the more gas will leave by this path.

Now we can talk about flow.

I mentioned before that we built up pressure in the manifold by making it harder for the gas to leave. This happens when you take away some energy from the moving gas, since we have taken something away in order for everything to balance out we have to put it back in somewhere ie. we have to push the gas harder to make it flow.

There are several ways we can take energy away from our moving gas. The one we discussed before was the turbo. The turbo is taking away some of the energy stored in our fast moving gas and using it to spin the turbine. Other places this happens is in friction as the gas rubs against the walls of the pipe, and friction losses in turbulence if we make the gas flow over something uneven or through a small hole.

We want to make the restriction in the wastegate route as low as possible, so we can get as much gas as possible to go out this way. We do this by making sure there are not many things which are taking energy away from our gas, ie. no turbos, no sudden changes in direction, no small diameter pipes, and no uneven bits which make turbulence.

And this is where we come to the 'design' side of things. The first section of the wastegate route is arguably the most important, because if we cock up this bit then it doesnt matter how beautiful everything looks further down the path. This rather important 'beginning' bit is the junction where the wastegate path splits off from the rest of the manifold.

Before we move on there is one last thing to mention: boundary layers. Unfortunately this may be a bit tricky without pictures, but I will do my best.

A boundary layer is the layer of fluid near to a bounding surface. For pipe work this bounding surface is usually going to be the wall of the pipe. Whenever you have fluid (in this case our exhaust gas) flowing through a pipe a boundary layer forms at the wall. This boundary layer moves slower than the rest of the gas in the pipe as it has to deal with the friction from rubbing on the pipe, and turbulence generated by any imprefections. The end result of this boundary layer is that the amount of gas we can flow through the pipe is slightly less than we would expect since the boundary layer has effectively reduced the diameter of our pipe slightly.

In this situation the gas doesnt have to make much of a change in direction to get to the wastegate. The flow path is nice and even, there will be minimal energy loss as the gas takes the route to the wastegate. The boundary layer at the Y junction will be more or less the same as the boundary layer in the straight pipe. As a result the gas going down this path dooesnt need to be pushed very hard, so lots of gas will go to the wastegate instead of to the turbo. Just what we were after.

Option 2:
Acceptable.

To get the the wastegate the gas does have to make a change in direction and the boundary layer here is going to be a little different. The gas is coming from the left and heading to the right, and as it starts to head down the wastegate path it overshoots the corner a little. This creates a little spot just on that corner where the boundary layer is a bit bigger, and the effective diameter of the pipe is a bit smaller.

Remembering what we said before about smaller pipes presenting more restriction, we can see that this is going to have slightly more resistance to the gas flow than Option 1. The end result is that a little bit less gas will take our wastegate route and a little bit more will take our turbo route: our wastegate just became a little bit less efficient.

This image shows flow through an intercooler. See in the bottom left where the gas coming in from the charge piping overshoots the corner and creates a 'bubble' of swirling gas which goes nowhere

http://www.are.com.au/inter/ic001n.JPG

Option 3:
Not so good.

Here the gas which is going to flow to the wastegate has to make a reasonable change in direction. The gas is going to overshoot the corner just like it did in option 2, but this time it will go further. The 'bubble' of slow moving gas will be bigger and the effective diameter of our pipe will be smaller. We have more restriction and reduced flow: less gas is able to take our wastegate route.

Option 4:
Rubbish.

Same principles as before but even worse for flow. Gas has to make a big change in direction to go down our wastegate route. The overshoot on the corner will be huge, making a really big bubble of slow moving gas on the corner. The effective diameter of our pipe has been reduced significantly and the flow to our wastegate is reduced also. This style of wastegate route is unlikely to be able to flow enough gas to hold our target boost pressure as there is not a big enough difference between the restiction provided by the turbo and the restriction provided by the wastegate route.

So what can we do about it?

We can attempt to rescue a poorly designed manifold by fitting a large wastegate. By making the wastegate piping really big we can compensate for the reduction in effective pipe diameter created by the boundary layer in options 3 and 4. This does work to a certain extent though you will find your self having to buy much more expensive parts.

We can also try to reduce other sources of energy loss in the wastegate route by making the down pipe after the wastegate valve bigger, or by reducing the number of tight bends the down pipe has to make.

One other thing to note is where turbo sizing comes in to this. The bigger your turbo is, the less of a restriction it presents to the exhaust gas (this is where your power increase comes from when you put a bigger turbo on). This means that all of the design issues mentioned above become even more critical because the wastegate must be super efficient to get enough gas flow away from the turbo.

This is part of the reason why car manufacturers get away with really horrible looking wastegate plumbing, because the factory turbo is so small it presents a large restriction and the wastegate doesnt need to be all that efficient to still recieve adequate gas flow.

And there we have it. That is about as best as I can explain it. If I find some decent pictures I will add them to the post.

anymore input is welcomed.

I see my manifold is option 3, straight 90.

BoostedK20

01-29-2013, 11:30 AM

Great information. Repped :thumb:

boosted_teg

02-01-2013, 12:27 PM

Here's a little more to add.

Wastegate feed quality is extremely important for street cars that wish to run oversized compressors at low efficiency ranges.

A properly designed manifold should favor the wastegate no less than 40% or so, especially when used with a super-flowing engine combination, and a larger exhaust-side on the turbocharger.

Let's take a quick look at what happens when you design a manifold with a 90-degree sharp turn welded onto a collector

As you can see, exhaust gases have the tendency to blow right by the wastegate entry, rather than bypass the turbine.

Now, as long as there is a larger amount of restriction in the exhaust housing, exhaust gas will "back up", so to speak, and be more inclined to evacuate through the path of least resistance, which in that case would be the wastegate.

Spaz

02-01-2013, 02:10 PM

what was that new manifold made with the ultimate wastegate placement?

PetefromtheStreets

02-02-2013, 12:12 AM

JBL I believe.

boosted_teg

02-02-2013, 02:24 AM

JDL makes the maniflld that has the best wastegate placement. I have yet to see anyone hit the dyno with thie manifold, but it is neat.

Vit's turbo manifold is similar to that, just isn't v-band, but the wastegate placement is almost identical. He can use a 3 psi wastegate spring and boost creep at all, all the way to redline, with a turbo larger than a 15'' mac book.

boosted_teg

02-05-2013, 01:34 AM

Got a picture of Vits turbo manifold? Ive never seen his car/motor. Id absolutly LOVE to have 0 creep.

i never saw a 4 bolt to vband before. Youde have to bolt that to the exaust housing of your turbo, which would drop the turbo even lower. I dont know why jdl just doesnt make a 4 bolt instead of the vband

PetefromtheStreets

02-05-2013, 09:04 AM

i never saw a 4 bolt to vband before. Youde have to bolt that to the exaust housing of your turbo, which would drop the turbo even lower. I dont know why jdl just doesnt make a 4 bolt instead of the vband

That flange looks quite slim so it would only drop it by what looks like less then half an inch. But I'm sure it's made to a vband to be able to adjust the turbo at whatever angle you see fit to allow it to work on numerous setups.

Si Speed 317

02-05-2013, 11:01 AM

VitViper

aLmk

02-05-2013, 11:30 AM

myvtecbroke.com is vits build blog.

boosted_teg

02-05-2013, 01:31 PM

thanks almk!

boosted_teg

02-05-2013, 01:54 PM

http://www.go-pwr.com/sites/default/files/rotator-images/P1000063.JPG

wonder if these are for sale.

aLmk

02-05-2013, 04:32 PM

That's his! And I highly doubt you could get one.... You do have to get rid of the evap to fit his manifold.

boosted_teg

02-05-2013, 09:18 PM

mines in an integra chassis, i got tons of room everywheres. Its perfect design, i bet theres zero boost creep

aLmk

02-05-2013, 10:58 PM

Ya he can hold 3 psi to redline on a huge turbo.

boosted_teg

02-06-2013, 01:14 AM

amazing boost control. im jealous

VitViper

02-06-2013, 03:52 AM

It doesn't hold exactly 3psi as the turbo is large and doesn't want to make 3 psi (most turbos have a minimum amount of boost they like to make even if you have ideal WG placement, but if WG placement is poor you push that threshold very high up -- I've seen K20 turbo kits that want to make 9psi on a 3psi WG spring because the manifold/WG placement is garbage).

That being said -- in cold weather (30-40* F) I make about 4.5psi (maybe 5psi at 8800 rpm), in warm weather (70+) it makes just about 4psi even at redline/rev limit. Keep in mind this isn't creep -- the turbo will hit 3psi @ 4k rpm and SLOWLY climb to 4.5psi @ rev limit (think supercharger boost).

This is as perfect as it's going to get with the size of turbo I'm using. Then again most turbos that I've seen don't really want to spin for less than 4psi with ideal WG placement, and the WG spring is not "PSI", a 3psi WG is usually something like a .22-.25 bar spring, meaning with denser ambient atmosphere it's actually closer to a 4psi spring than a 3psi spring (hence the boost flux I see between cold/hot weather running on pure WG).

All that being said, I can turn on the boost control just a tad and make a flat 6-8psi in 2nd gear from 4700 to 8800 rpm (depending how much I want to run), to as much as 25psi -- I haven't pushed the setup much past that, but 23psi at the track was only 44% duty cycle or so on my boost control. So safe to say 30psi+ on a 3 psi spring is possible ;)

I've seen K20 turbo kits that want to make 9psi on a 3psi WG spring because the manifold/WG placement is garbage).

Blame Mo, not me. I just wanted a top mount. He said it wouldn't creep. :beer::banghead:

aLmk

02-06-2013, 10:26 AM

Well I was slightly mistaken :giggle:

VitViper

02-06-2013, 05:09 PM

Blame Mo, not me. I just wanted a top mount. He said it wouldn't creep. :beer::banghead:

It's not just you... the list continues to grow.

PetefromtheStreets

02-06-2013, 08:37 PM

VitViper that manifold looks so sick. The size alone is making me think of going turbo instead of my charger.

BoostedK20

02-08-2013, 12:47 PM

Stickied this thread :thumb:

boosted_teg

02-09-2013, 12:37 AM

VitViper is this manifold availible to the public or was it custom to you?

PetefromtheStreets

02-09-2013, 12:51 AM

VitViper is this manifold availible to the public or was it custom to you?

From lookin at the picture you guys had posted it said "burns" on it. So I'm assuming 1 of 2 things.

1) they used a burns collector and gabbed the rest or

2) burns stainless made it.

Either if which are pretty freakin boss!

I'd love to get one of those. Makes me want to sell my stuff and go huge turbo. Lol

Si Speed 317

02-09-2013, 01:00 AM

From lookin at the picture you guys had posted it said "burns" on it. So I'm assuming 1 of 2 things.

1) they used a burns collector and gabbed the rest or

2) burns stainless made it.

Either if which are pretty freakin boss!

I'd love to get one of those. Makes me want to sell my stuff and go huge turbo. Lol

IIRC, Jeff at GO-Power made this manifold. He used the orange 'legos' as a mock-up template instead of welding and redoing and rewelding etc. Then he made the manifold. I guess the collector is a Burns collector.

PetefromtheStreets

02-09-2013, 01:02 AM

IIRC, Jeff at GO-Power made this manifold. He used the orange 'legos' as a mock-up template instead of welding and redoing and rewelding etc. Then he made the manifold. I guess the collector is a Burns collector.

From talking with Vit, he had mentioned go-power once before so that's probably right. And I was partially right. Burns collector it is. Lol

boosted_teg

02-09-2013, 01:34 AM

id definetly ditch my manifold for someone that doesnt have creep without having to switch to a Vband.

I guess im just going to have to modify the wastegate port, or add another 44mm gate on the top. arrgg

aLmk

02-09-2013, 02:04 AM

Yes go power made the turbo setup.

VitViper

02-09-2013, 04:08 AM

It's a completely custom one-off hand made piece. Jeff won't make another one, it's made of 321 stainless using the burns collector. I think materials alone were like $1000-1200.

VitViper

02-09-2013, 04:13 AM

id definetly ditch my manifold for someone that doesnt have creep without having to switch to a Vband.

I guess im just going to have to modify the wastegate port, or add another 44mm gate on the top. arrgg

There are two things (well technically three) you can do to reduce/eliminate creep if you cannot custom weld a manifold with proper WG placement.

1) Recirculate the dump tube into the downpipe. This will help cut down on the creep
2) Add a second wastegate to the other portion of the manifold where the runners don't feed the first gate well (if at all honestly).

You could even do both 1 and 2 (option 3 lol).

I personally absolutely dislike most of these production manifolds that use one gate with absolute crap placement for the gate. The other thing that really gets me is these companies will go out and say "it doesn't creep". The fuck it doesn't... one glance at the WG placement and it doesn't take a rocket scientist to tell you the potential for creep is really high.

boosted_teg

02-09-2013, 12:15 PM

Thanks Vit.

I didnt think recirculating would help calm down creep. Is this because of the extra exaust pressure which will create more backpressure? Just guessing, but this would probably slow down spool time and reduce power?

I agree with you about companys claiming no creep. If i had of known what i do now 2 years ago, i wouldve bought a good manifold or had one custom made.

I think im going to do with option 2. I definetly have little wiggle room to modify the wastegate now.

boosted_teg

02-10-2013, 03:51 AM

saw this on a few cars. Its different and never saw it done on a honda/acura, mainly supras (along with others im sure)

http://img88.imageshack.us/img88/2940/img0318zo6.jpg

aLmk

02-10-2013, 08:35 AM

Hmm that looks like it would work quite well. However I doubt that would fit on my chassis (fa5)

boosted_teg

02-10-2013, 01:07 PM

ya or even my dc2 without having a brake booster delete

umdorado

02-16-2013, 07:38 PM

So where i am at? lols.

boosted_teg

02-16-2013, 11:04 PM

that to me looks half decent. Its not a 90" turn with a sharp edge so it shouldn't creep a whole lot. The tune and your turbo will also affect it.

What yours looks like is what im doing to mine with a 90" weld el

2006ninjasi

02-17-2013, 02:20 PM

Srt v2 uses a "tear drop" wastegate with smooth transition from manifold to wastegate, but it still creeps. Can anyone shed some light on this?

boosted_teg

02-17-2013, 08:01 PM

couple pages back vitviper explains creep. It depends on a few other factors also

aLmk

02-17-2013, 08:12 PM

Srt v2 uses a "tear drop" wastegate with smooth transition from manifold to wastegate, but it still creeps. Can anyone shed some light on this?

My understanding is that method helps considerable especially for cars like the 8thgen where it is tough to get a good wastegate placement unless you have a super manifold like Vit's or use 2 wastegates to make sure all sides of the collector are covered, but this tear dropping doesn't fix the creep completely.